Jewelry chains in general are well known, as are chains with diamond cut facets. Chains having round solid links present no major problem in cutting the facets, since the link wall is partly cut away and the depth of the cut can vary, allowing a certain tolerance as to the amount of metal that is removed. The surface area created by the cutting away of part of the chain link provides the facet, which surface area is dependent on the amount of metal cut away. Thus there are known solid jewelry chains of all types with diamond cut facets as, for example, diamond cut rope chains, diamond cut Garibaldi chains etc. One way of diamond cutting solid chains is by using a so-called ice lathe. This method is well known and was already disclosed in U.S. Pat. No. 3,083,002 to Lacey and U.S. Pat. No. 4,754,535 to Valtiero, among others. This method is as follows. A jewelry chain is wound tightly around a hollow drum held between the centers of a universal lathe. The ends of the chain are secured to a fastner on each end of the drum. The drum is rotated and a freezing medium, such as glycol, is circulated from a refrigerating unit to the inside of the drum. As the temperature of the drum drops with the chain wound round it, cold water is sprayed on to the drum's surface and is almost instantaneously frozen as it contacts the surface of the drum. The frozen water thus surrounds the chain in contact with the drum, freezing the chain links in place and immobilising the chain. In fact, only a small portion of each chain link has to be frozen in order to immobilise the whole chain, since the entire chain is held firmly and immobilised, if at least part of each link is embedded in ice.
Once the chain is immobilised, a diamond cutting tool can be applied to the chain as it rotates on the drum, cutting off the outermost sections of the links, thus producing diamond cut facets. The deeper the cut, the larger the facet. This is all good and well for solid chains. However, this is not applicable to diamond cutting facets on chains made with hollow annular links. Such hollow links generally have a very thin outer metal shell in the range of 0.05 mm to about 0.2 mm. Annular or curved hollow links with such thin walls present a serious problem if one wishes to impart to the link a diamond cut facet, since cutting into the curved section of the link will produce a hole rather than a flat surface.
My U.S. Pat. No. 5,303,540 proposes one solution for preparing diamond cut hollow chains and chain links by providing the link with diamond cut surface areas in the shape of the outer contour of the link, i.e. where only the outer wall of the hollow chain link is shaved without deforming the wall or cutting into it. Diamond cut facets on curved sections of the links will, therefore, not be flat, but rather curved in accordance with the curvature of the link at the place of the facet.
U.S. Pat. No. 5,125,225 to Strobel discloses a method for making diamond cut flat facets on hollow rope chains, including chains having seamed hollow links, having the same appearance as in the classical diamond cut rope chain. This is accomplished by first flattening the curvature on the round links and then diamond cutting the flattened surface. In order to achieve the flattening of the links, the patent uses the ice lathe method to immobilise the rope chain by winding the chain around a refrigerated drum and freezing the chain in place. The frozen chain is then incrementally burnished as it is rotated to impart to the individual links flattened surfaces. These surfaces are then diamond cut while the chain is still immobilised to give sparkling flat facets. Strobel thus applies the known ice lathe technique to hollow rope chains having annular links to immobilize the hollow chain by embedding it in an ice mould. The Strobel patent is directed to hollow rope chains with annular links.
In both cases, whether diamond cutting solid or hollow rope chains with annular links, it is sufficient to freeze only a small part of each annular link in order to immobilise the whole chain and prevent it from moving. In the case of hollow rope chains, only the lower half of the chain is embedded in ice near the drum surface, since if one were to cover the entire chain with ice it would be difficult to form a flat indentation in the annular link, because solid ice formed inside the hollow link would resist the deformation of the link wall. In any event, immobilising chains with annular links is quite simple and does not require a high level of exactness when freezing the chain. Consequently since immobilising a rope chain and all its annular links is relatively simple, it makes it possible to burnish the hollow annular link chains precisely to a predetermined depth to form flat facets which can then be diamond cut, while the chain is still immobilised, without cutting into the thin link wall.
There are a number of chains, however, not rope chains, that are made with spiral links, in which each link is in the form of a coil with more than one turn. Such links can comprise X+Y turns, where X is an integer, preferably from 1-5 and Y is an integer or a fraction. Chains with coiled links intertwined with one another have the coiled links oriented in such a way that their central axis is diagonal to the axis of the chain length. One popular chain of this kind, called a Garibaldi chain, comprises sections of chains made with coiled links having one and three quarter turns. Coiled chains, such as the Garibaldi chain, are also known to have diamond cuts, but this is only where the chain is made of solid coils. The coiled links inherently have a certain degree of springiness and thus can oscillate when touched. In the case of chains with solid coiled links, this oscillation does not prevent diamond cutting flat facets, since such facets are cut to substantial depths into the solid link wire, so that even if the coil link oscillates somewhat, for example 0.01 mm, in a coil having a wire diameter of 0.5 mm it does not siginificantly affect the facet, which is cut substantially deeper into the wire than the 0.01 mm. In other words, cutting facets in coiled link chains is possible when the links are solid. This is not the case with hollow coiled link chains. When attempting to make diamond cuts in hollow coiled link chains, conventional freezing of the chain by the ice lathe method leaves portions of coils unfrozen, resulting in slight oscillation of the coils, which is detrimental to flattening and diamond cutting the thin coil walls. Attempting to make flat diamond cut facets by conventional freezing of hollow coil link chains results in at least some of the flat surfaces of the coil links having their walls perforated due to the angular orientation of the coils with respect to the chain length and their oscillation. Freezing the chain on the drum in the conventional manner does not prevent the oscillation of the coil. If one were, on the other hand, to embed the entire chain in ice, this would prevent uniform flattening and diamond cutting because of the ice formed inside the hollow part of the coiled link and also on the top surface of the coiled link.